The chemical species, 1-(2′-Deoxy-2′,2′-difluoro-D-ribofuranosyl)-4-aminopyrimidin-2-one of Formula (II) is generically known as Gemcitabine.

Gemcitabine of formula (II) a pyrimidine analog, is structurally similar to cytarabine, but has a wider spectrum of antitumour activity due to its different cellular pharmacology and mechanism of action. Gemcitabine belongs to the group of medicines called antimetabolites. Gemcitabine is a type of chemotherapy for treating many types of cancers including lung, pancreatic cancers. It can interfere with the growth of rapidly growing cells like cancer cells and causes cell death.
Isolation and crystallization of Gemcitabine hydrochloride disclosed in U.S. Pat. Nos. 4,526,988 and 4,808,614, adopts laborious chromatographic purifications in different stages which make the process industrially nonviable.
The process disclosed in U.S. Pat. No. 5,637,688 for the isolation and crystallization of Gemcitabine hydrochloride comprises following steps:                a) Deblocking of β-1-(2′-deoxy-2′,2′-difluoro-3′,5′-di-O-benzoyl-D-ribofuranosyl)-4-aminopyrimidin-2-one with a catalytic amount of an alkylamine in the presence of methanol or ethanol in an environment essentially free of water;        b) Treating the resulting solution with hydrochloric acid and an antisolvent selected from the series of acetone, acetonitrile, tetrahydrofuran, propanol, butanol, isobutanol, sec-butanol and isopropanol;        c) Purifying the resulting Gemcitabine hydrochloride.        
In EP0630905, isolation involves dissolution of Gemcitabine hydrochloride (1:1) in hot water and then precipitated by acetone to get 80% β-anomer rich product which is further purified by re-dissolving in hot water and then again precipitated by acetone to get 99% β-anomer of Gemcitabine hydrochloride.
It also describes isolation of Gemcitabine base of 99% purity from Gemcitabine or its addition salt by dissolving in hot water and increasing pH to 7-9 isolating Gemcitabine of 99% and is further converted into Gemcitabine hydrochloride.
WO2005/095430 discloses the isolation of Gemcitabine hydrochloride whereby crude 2′-deoxy-2′,2′-difluorocytidine base is dissolved in isopropanol and then precipitated by hydrochloric acid and filtered off. The solution so obtained is then further purified by water and acetone as solvent system which is already reported in prior art. The process of purification disclosed in WO2005/095430 includes dissolving Gemcitabine HCl in water to increase the purity and then again dissolving in water and acetone for further purification thereby increasing the unit operation.
Therefore there is a long felt need of a process for the isolation and purification of Gemcitabine hydrochloride, which is selective for the beta-anomer of the Gemcitabine hydrochloride giving high yield and purity.
Also there is a need of a process of purification which does not require any reversion of hydrochloride to base by adding other bases like alkyl amine and again converting back to hydrochloride salt which increases unit operation without giving appreciable yields or a process of purification which does not require any pH adjustment as disclosed in prior art.